Can m4/3 cameras front- or back-focus?

Are m4/3 cameras inherently incapable of front- or back-focus? Phase-difference DSLRs certainly are subject to this problem.

This quote from the Panny G5 product page seems to imply that they are immune:

"The phase-difference AF system is susceptible to mechanical margin of error. However, in the contrast AF system, focusing is controlled by the image sensor so that no mechanical margin of error occurs to achieve precise focusing."

If so, this would seem a very major advantage of the m4/3s system, not having to try to fine-tune focus for all your lenses.